I'd been out a for a ~14.5km run, uploaded the run, then ~30 minutes later put the watch on to charge, however it showed no sign of charging.

I've tried it in with 2 separate cradles/docks. 4 different USB ports (on 3 different machines) 2 different chargers. (no USB communications required to get power) 4 different USB cables

The still had some charge left (1 bar), and was working when it was placed in the charging cradle (which indicates the failure was NOT due to dead battery provision or shunt problems).The temperature was ~18 degree C, above the minimum battery charging temperature (0 degrees), and well below the maximum charging temperature.

I had a similar issue with it not charging and I ended up having to pull the dock apart and get some sewing machine oil and a sewing pin on the charging pins. I simply dropped a little oil on the charging pins and then used the sewing pin to depress the charging pings until they loosened up and popped out. Once they were all out then the watched has been charging np since.